WO2014080129A1

WO2014080129A1 - Augmented-reality optical module

Info

Publication number: WO2014080129A1
Application number: PCT/FR2013/052812
Authority: WO
Inventors: Maxime DENEFLE; Zile Liu
Original assignee: Laster
Priority date: 2012-11-21
Filing date: 2013-11-21
Publication date: 2014-05-30
Also published as: US20150301336A1; CN104903777A; EP2923233A1

Abstract

The invention relates to an augmented-reality optical device (1) characterised in that it comprises: a display (2) for emitting at least one image in the form of a beam; an optical surface (4) arranged essentially transversely to said main optical axis such that it deflects the image towards the eye; a semi-reflective plate (3) for deflecting the image between said display and said optical surface; and a polariser (6) for eliminating the parasite light.

Description

OPTICAL MODULE OF INCREASED REALITY.

The present invention relates mainly to the field of portable augmented reality optical devices, in particular those mounted on the head of a user.

There are currently many solutions for image viewing by a display system mounted on the head of a user. A majority of these devices do not allow vision by transparency and therefore can not be integrated into an augmented reality system without significantly reducing the natural field of view of the user which represents about 180 ° for the natural field of view and 120 ° for the natural field of vertical view.

Some optical solutions are transparent but they use an "off-axis" optical path, that is to say outside the main axis of vision of the user, which induces strong optical aberrations, in particular astigmatism, curvature of field and distortion, which reduces the quality of the projected image in the retina. In order to compensate for these aberrations, these devices use a certain number of optical elements that are not compatible with the fineness required for a device that one wishes to be able to integrate into an ergonomic pair of glasses. Another problem with current devices is the size of the exit pupil. The pupil of an eye looking at a projected image of average intensity is about 3mm in diameter. In order to have an ergonomic display system, the exit pupil, that is to say the area of placement of the eye where the user perceives the whole field, must be at least 3 times larger. that the pupil of the eye of the user so that even if the user moves with respect to the system, he continues to perceive a sharp image without vignetting. The object of the invention is in particular to propose a device whose size and complexity are considerably reduced with regard to the existing display systems and designed so that it can be fixed to the head of a user while remaining transparent for her stare. In addition, such a device will be advantageously easy to use for consumer applications where ergonomics and simplicity are key elements.

According to the invention, such an augmented reality device is characterized in that it comprises:

a display for transmitting at least one image in the form of a beam;

means for positioning said display laterally relative to an eye of a user, so that said display emits said image substantially transversely relative to a main optical axis of said eye;

an ocular return diopter disposed substantially transversely to said main optical axis so that it returns the image in the direction of the eye;

means for redirecting said image between said display and said diopter; and,

polarization means for eliminating stray light. This device may further comprise ophthalmic correction means for adapting the image to the vision of the user.

The display is preferably chosen from LCD, OLED and LCOS types. The device may further comprise at least one lens or a group of lenses disposed downstream of the display and upstream of the redirection means, in particular to obtain a desired magnification of the image, preferably by compensating for chromatic aberrations.

The redirection means are advantageously a flat or curved semi-reflecting plate, designed to fold the image beam from the display towards an inner face of the diopter, said blade passing without reflection at least part of the beam reflected by said diopter. This semi-reflecting blade comprises a polarizing structure capable of providing the reflection and transmission functions of said blade on one side and significantly reducing the parasitic reflections due to the light coming from the other side of the beam. said blade.

It may also include a micro-camera whose axis is placed substantially parallel to the optical axis of the user's directing eye, an inertial unit, a magnetic compass and a GPS to allow a virtual interaction with the user. environment observed in augmented reality according to the movements and the point of view of the user. Preferably, the device also comprises a battery and electronic computing and communication means designed to allow wireless use with a smartphone or a computer.

The invention also relates to an augmented reality optical system characterized in that it comprises two augmented reality optical devices according to the invention, each for a respective eye of the user. A device or system according to the invention advantageously comprises a load-bearing structure for fixing it to the user's head, preferably of the spectacle frame type, ski mask, protective mask or helmet.

Several embodiments of the invention will be described below, by way of non-limiting examples, with reference to the appended drawings in which:

- Figure 1 schematically illustrates a vertical axial section of a device according to the invention; and,

FIG. 2 illustrates a section through the thickness of a semireflecting plate for the device of FIG. 1.

Figure 1 uses an optical device 1, portable, and intended to provide augmented reality to a user of this device. This device is in an optical configuration called "on the axis", that is to say along an optical axis XI which is substantially the axis of the user's gaze when looking at infinity, in front of him ; this reduces the complexity and weight of such a device. In the example illustrated, this device 1 comprises a display 2, a semi-reflecting plate 3, a diopter 4, a retardation plate 5, a polarizing film 6 and ophthalmic correction means 7.

The display 2 may be of the micro-display type ("microdisplay"), LCOS, LCD or OLED; it is intended to form and emit an image, fixed or animated, in the form of a light beam. The reflective plate 3 is of the PB S type (Polarizing Beam Spliter Plate, in English) is used to fold the optical path of the light beam from the display 2 towards the diopter 4. The diopter 4 is a semi-transparent catadioptric element intended to collimate the beam so as to project the image to infinity in the eye 10 of the user. The retardation plate 5 is a polarized plate of the quarter-wave type.

The blade 3 is transparent for polarized P-type light, that is to say polarized in the plane of incidence, and reflects S-polarized light, that is to say perpendicular to the plane of incidence. , when it is positioned at 45 degrees to the optical axis XI. The display 2 comprises means of polarization or is juxtaposed with a polarizer, so that the emitted light is polarized S, so that it is reflected by the reflecting plate 3. Once reflected by the reflecting plate 3, this light It crosses the retardation plate 5 which converts the S polarization of the light into a circular polarization. The reflection on the semi-reflecting mirror formed by the diopter 4 reverses the orientation of the circular polarization and the second passage in the quarter wave plate converts the light into polarization P; thus, the semireflecting blade 3 becomes totally transparent for the light reflected by the diopter 4, when this light returns it towards the eye of the user.

An assembly, not represented in the figures, consisting of optical lenses coupled to a semi-reflecting catadioptric element, intended to obtain a desired magnification while compensating for chromatic aberrations, is placed immediately downstream of the display 2.

Thus, the optical path traveled by an image transmitted by the broadcaster 2 can be described as follows:

Display 2 set lenses

semi-reflective blade 3

¼ wave blade 5

dioptre 4

¼ wave blade 5 Eye 10 The optical path traveled by a scene 11 observed by the user through the device 1 can be described as follows:

Scene 11 → Diopter 4

→ ¼ wave blade 5

→ semi-reflective blade 3

→ polarizer 6

→ Means of correction 7 → Eye 10

The use of a semi-reflective plate 3 of the PB S type, instead of a semi-reflective mirror type plate, significantly increases the brightness of the device when the display is of the LCD or LCOS type. The light transmission ratio for the optical path of the device of FIG. 1 is 77% with a PBS blade against 25% with a semi-reflective mirror. A semi-reflective mirror may nevertheless be used for a lower cost architecture.

The use for the diopter 4 of a semi-reflecting catadioptric element 4 in the frontal position makes it possible to compensate for the spherical aberrations and does not add any prismatic effect or distortion when the user looks through the device. The interest of such catadioptric elements is the possibility of using large diameters without increasing the chromatic aberrations as with the refractive elements. The use of a spherical or aspheric diopter coupled to the flat or semi-reflective curved blade also makes it possible to significantly increase the display field. The diopter 4 is preferably made of polycarbonate with a semi-reflective inner surface 14, which can be aspherical, to optimize them. performance. The internal transmission of the diopter 4 is optimized to ensure a good contrast between the projected image and the scene 11 observed. Semi-reflective holographic processing can be used instead of thin-film semi-reflective processing to improve the brightness of projected images when projecting a monochromatic or RGB image. The outer face 15 of the diopter 4 is calculated to cancel the prismatic effects for the vision in transparency, thus the natural vision of the scene 11 by the user is preserved. The retardation plate 5 may take the form of a polymer film. To facilitate the assembly of the device, it can be thermoformed to directly adapt to the curvature of the diopter 4.

The geometry and the curvature of the inner surface 14 of the diopter 4 and those of the lenses of the assembly coupled to the diffuser can be optimized to adapt the magnification of the optical system to different screen sizes of the diffuser 2.

FIG. 2 illustrates a section along the thickness of the semi-reflecting plate 3. In the example shown, from a first face 17 facing the display 2 and the diopter 4, and a second face 18 facing the eye 10 of the observer, the blade 3 comprises 6 layers 21-26 which are:

a polarizing and reflecting structure 21 constituted by a film of the type

WGF;

an adhesive 22 for the first layer 21 on the third layer 23;

a polymer substrate 23, for example a PMMA or a polycarbonate;

an adhesive 24 for the fifth layer 25 on the third layer 23;

a layer formed of a linear polarizer 25 with a high transmission coefficient; and, an antireflection coating 26.

A parasitic light which would have come from below the device (reflection on the semi-reflecting plate 3) passes through the antireflection coating 26, the polarization S is absorbed by the polarizing film 25, the residual polarization P passes through the substrate 23 without being reflected by the film GF which transmits the polarization P and reflects the polarization S. In this way, such a parasitic light is no longer reflected towards the eye 10 of the user. The polarizer 6, although not essential, can be placed on the path between the semi-reflecting plate 3 and the user's eye 10, in order to advantageously filter the non-polarized portion P of the light which would be produced by a parasitic reflection on the semi-reflecting plate 3 if it does not include the structure 17. In the example illustrated in FIG. 1, the polarizer 6 is a film advantageously deposited on the correction means 7, making it possible to adapt the image to the vision of the user.

A device such as that of Figure 1 has a very small footprint, the eye relief ("eye relief" in English) is 15mm; the complete device 1 may have a size of 30 x 25 x 17 mm; it is for example completely integrable in a pair of ergonomic sunglasses. In addition, a device according to the invention represents an improvement over the state of the art through the use of a semi-reflective plate coupled to a semi-reflective spherical frontal surface 14 which significantly reduces aberrations and vignetting of the natural field of view. The exit pupil is also easily increased from 9mm to 15mm in diameter depending on the version of the architecture. With an exit pupil with a diameter greater than 9 mm, such an optical device 1 can be used in pairs so as to produce a small binocular augmented reality device. This system would for example be easily compatible for a population group with an IPD ("interpupillary distance", inter-pupillary distance, in French) between 52 and 65mm without requiring any adjustment.

The micro-display 1 is located above so that the natural field of view of the user is preserved; consider HFOV (horizontal) natural at least 160 ° and VFOV (vertically) greater than 100 °. The device 1 does not reduce the natural field of view while having a reduced form factor, so it can be used in a large number of applications where the perceived scene is as important as the information or projected images.

The device can advantageously be coupled to a micro-camera or motion sensors linked to the user's head (gyroscopes, accelerometers, etc.) so as to interact with the observed scene. Other options such as voice recognition, an inertial unit or a tracking device (GPS ...) can be added to improve the immersion and user experience.

Of course, the invention is not limited to the examples which have just been described. Thus, the device may not include ophthalmic correction means. In the case where a correction is used, the ocular clearance is reduced by a few mm. The correction can be applied directly to the semi-reflective frontal glass or by adding ophthalmic clips. Also, the choice of the display used among types LCD, OLED or LCOS is done according to the needs of the intended application, in terms of brightness, color rendering and costs.

Instead of an optical lens assembly coupled to a semi-reflective catadioptric element for achieving the desired magnification while compensating chromatic aberrations, these lenses can be replaced by hybrid lenses coupled with a Fresnel lens. In the case of high volume production, these components can be molded in polycarbonate to optimize costs.

Instead of being above the optical axis of the user's eye, the display may be disposed laterally relative to that axis, for example on one side or below.

Claims

claims

An optical device (1) of augmented reality, characterized in that it comprises:

a display (2) for emitting at least one image in the form of a beam;

- Means for positioning said display laterally relative to an eye (10) of a user, so that said display emits said image substantially transversely relative to a main optical axis (XI) of said eye;

an ocular return diopter (4) disposed substantially transversely to said main optical axis so that it returns the image towards the eye;

means for redirecting (3) said image between said display and said diopter; and,

polarization means (6, 21, 25) for eliminating stray light.

2. Device according to claim 1, characterized in that it further comprises ophthalmic correction means (7) for adapting the image to the vision of the user.

3. Device according to one of claims 1 or 2, characterized in that the display is selected from LCD, OLED and LCOS types.

4. Device according to one of claims 1 to 3, characterized in that it further comprises at least one lens or a group of lenses disposed downstream of the display and upstream of the redirection means, in particular to obtain a desired magnification of the image, preferably by compensating for chromatic aberrations.

5. Device according to one of claims 1 to 4, characterized in that the redirection means are a semi-reflective plate (3), designed to fold the image beam from the display (2) towards a internal face (14) of the diopter (4), said blade (3) passing without reflection at least a portion of the beam reflected by said diopter.

6. Device according to claim 5, characterized in that the semi-reflecting plate comprises a polarizing structure (21) adapted to provide the functions of reflection and transmission of said blade on one side and reduce the other side so significant parasitic reflections due to light from the other side of said blade.

7. Device according to claims 1 to 6, characterized in that it comprises a micro-camera whose axis is placed substantially parallel to the optical axis of the eye direction of the user, an inertial unit, a compass magnetic and GPS to allow a virtual interaction with the environment observed in augmented reality according to the movements and the point of view of the user.

8. Device according to one of claims 1 to 7, characterized in that it comprises a battery and electronic means of calculation and communication designed to allow wireless use with a smartphone or computer.

9. Device according to one of claims 1 to 8, characterized in that it comprises a carrying structure for fixing it to the head of the user, preferably of the spectacle frame type, ski mask, protective mask or helmet.

10. Augmented reality optical system, characterized in that it comprises two augmented reality optical devices (1) according to one of claims 1 to 9, each for a respective eye of the user.